ML17199F890
| ML17199F890 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 07/11/2017 |
| From: | Carter J, Cowell M Flowserve Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML17199F890 (6) | |
Text
~ Flow Control Division Anchor/Darling Valves FLOWSERVE BWllP Valves Edward Valves Valtek Control Products Worcester Valves July 11, 2017 US Nuclear Regulatory Commission Document Control Desk .
11545.Rockville Pike Rockville MD 20852-27 46
Subject:
Stem-Wedge Separation of an Anchor/Darling Double Disc Gate Valve at Exelon, LaSalle County Station, Unit 2, February 2017.
Reference:
Flowserve, Raleigh 10CFR Part 21 Notification Letter dated February 25, 2013, Wedge Pin Failure of Anchor/Darling DD Gate Valve.
Attachment 1: List of Affected Customers and Plants Gentlemen:
This is to notify the US Nuclear Regulatory Commission that, in accordance with the provisions of 10CFR Part 21, we have gained additional insight and information concerning the referenced previously reported issue based on a recent incident at the
.LaSalle County Station, Unit 2 involving a similar valve.
Flowserve has been working with Exelon and nuclear industry groups to investigate and
- evaluate the stem-wedge separation in a size 12 class 900 Anchor/Darling motor-operated double disc (DD) gate valve. The valve stem was completely separated from the upper wedge, the wedge pin was sheared, the wedge threads stripped away and the pressed-on stem collar was pushed up leaving the valve inoperable. The valve operating thrust and torque is transmitted through the stem-wedge assembly, therefore separation of the stem and wedge will prevent the valve from opening and:can adversely affect closing. See Figure 1 for a sketch of the stem-wedge joint.
This incident is related to the wedge pin failure of a similar valve reported to the NRG under 10CFR21 on February 25, 2013. A wedge pin sheared on a 10-900 DD at TVA-Browns Ferry although the stem remained engaged in the wedge and the valve could be opened and closed. The conclusion in the evaluation of that incident was that wedge pin shear could lead to stem-wedge joint degradatior) and eventual stem-wedge failure similar to this incident at LaSalle.
Evaluation of this event added an element not addressed in the previous evaluation regarding the limitation of a pressed-on stem collar to support the actuator thrust and maintain the stem-wedge preload.
Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919*832-0525 1900 Smith Saunders Street Facsimile: 1-919*831-3369 Raleigh,' NC 27603 Page 1of5
Stem Wedge Separation AD DD Gate Valve 7/11/17 Review of the LaSalle incident concluded repeated valve cycles at high actuator loads eventually wore the wedge threads to the point of failure in shear during a valve closing cycle and subsequent separation of the stem from the wedge. Before thread failure the wedge pin sheared which allowed* stem to wedge movement with accompanying wedge thread wear and degradation. In additional the pressed-on collar was pushed up out of position, which would reduce or eliminate any existing preload in the joint. Wedge pin failure is attributed to both limited preload on the stem threaded section and exposure to actuator torques higher than the limit of the pin material. Since'stem-wedge preload
. can be reduced or removed by a stem thrust which exceeds the .stem-wedge joint capability, high thrust .can be a precursor for wedge pin shear for applications with wedge pins that cannot independently withstand the actuator stem torque. The capability to maintain the preload is much less for stems with pressed-on collars than for stems with ir,itegral collars.
- The scope remains the same as the previous notification, Anchor/Darling type DD gate valve with a threaded stem to upper wedge connection, typically size 2-1/2 inch and larger, operated by an actuator that applies torque on the stem to produce the required valve operating thrust. Note that most size 2 valves utilize a tee head stem connection, however while addressing the original wedge pin issue a few size 2 valves were discovered that have threaded stem connections.
Figure 1 Typical Double-Disc Gate Valve Trim SlEM COLLAR BODY Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow* Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 ~l'!fW JlQY!.Se Ole &.om Page 2 of 5
Stem Wedge Separation AD DD Gate Valve 7/11/17
- Valve evaluations and actions resulting from the previous notification are applicable and still apply. This notification includes additional information for maintaining the stem preload that was not addressed previously. The actuator thrust as well as the torque must be reviewed to insure the preload is maintained.
A loose connection is the result of inadequate stem thread preload whether not applied initially during assembly or not maintained during operation. The initial stem preload can be *reduced if the stem closing thrust in service is high enough to cause local 1 yielding of the joint. Stems with integral collars typically have allowable thrusts which do not govern the thrust limit of the valve however a stem with a pressed-on collar, supplied with many of the originally supplied valves, has a thrust limit which is less than the typical maximum allowed thrust values previously determined by weak-link or maximum thrust analyses.
Industry groups, such as BWROG, are determining appropriate corrective actions and priorities based on valve application. Consideration should be given to the following Flowserve recommendations:
Torque the stem into the wedge to the maximum joint capacity.
Replacement stems should have integral collars in lieu of press-on.
Replacement wedge pins are manufactured from high strength material.
Verify the actuator stem.thrust is less than the maximum allowed to maintain the
- stem preload.
- Attachment 1 is a list, based on our records, of customers, utilities and nuclear plants which were supplied with Anchor/Darling DD Gate valves with motor actuators on contracts with Sectio.n Ill and/or 10CFR21 imposed. This list added a few sites not included on the list provided with the original notification.
Flowserve plans to provide ea*ch of the customers identified in Attachment 1 with a copy
- of this nqtification letter.
I Please do not hesitate to contact us if you have questions or require additional information.
Respectfully s*ubmitted,
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~;rk Cowell
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Manager, Quality Assurance Engineering Specialist Flowserve Corporation, FCD Flowserve Corporation, FCD Raleigh, NC Raleigh, NC 919-831-3220 919-831-:3377 Flowserve US Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Oivision PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 \iY';\l';l/JLQW~E!!Y~.. cQ_m Page 3 of 5
Stem Wedge Sepa~ation AD DD Gate Valve 7/11/17 ATTACHMENT 1 ANCHOR/DARLING DOUBLE DISC GATE VALVES WITH THREADED STEMS AND MOTOR ACTUATORS AB/UTILITY NUCLEAR PLANT '
B&W THREE MILE ISLAND 2 BECHTEL ANO 1, CALLAWAY, MILLSTONE, SSES*, WOLF CREEK CFE LAGUNA VERDE COM ED DRESDEN, LASALLE, QUAD CITIES CPL BRUNSWICK, ROBINSON DOMINION SURRY DUKE CATAWBA, OCONEE DUQUESNE LIGHT BEAVER VALLEY* .
EBASCO. MILLSTONE I
ENTERGY GRAND GULF, NINE MILE, WATERFORD EXELON PEACH BOTTOM FPL CRYSTAL RIVER, ST. LUCIE GE BROWNS FERRY; BRUNSWICK, CHINSHAN, CLINTON, COLUMBIA, CONFENTES GE COOPER, DUANE ARNOLD, FITZPATRICK, FORT CALHOUN, FUKISHIMA GE GRAND GULF, HATCH, KUOSHENG, LAGUNA VERDE, LASALLE, LIMERICK GE NINE MILE, PEACH BOTTOM, PERRY, PILGRIM, RIVER BEND, SHIMANE GPC HATCH GPU OYSTER CREEK GULF STATES RIVER BEND ILL POWER CLINTON INDIANA MICH POWER COOK MAINEYANKEE MAINEY ANKEE NEU MILLSTONE NIAGARA MOHAWK NINE MILE NORTHEAST NUC MILLSTONE I
NPPD COOPER NSP MONTICELLO, PRARIE ISLAND NYPA FITZPATRICK ONT HYDRO BRUCE PG&E DIABLO CANYON PHILA ELECTRIC PEACH BOTTOM PPL SSES PROGRESS ENERGY ROBINSON SCE SAN ONOFRE (
SCE&G VCSUMMER ..
Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Conlrol Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com.
Page 4 of 5.
I_
.Stem Wedge Separation AD DD Gate Valve 7/11/17 SNCLAVALIN BRUCE TPC CHINSHAN, KUOSHENG, LUNGMEN TVA BROWNS FERRY VEPCO NORTH ANNA, SURRY VERMONT YANKEE VERMONT YANKEE WESTINGHOUSE COOK, DIABLO CANYON, GINNA*, INDIAN POINT, KANSAI ELECTRIC, WESTINGHOUSE KORI 1, NORTH ANNA, POINT BEACH, PRAIRIE ISLAND, RINGALS, KEWAUNEE, WESTINGHOUSE ROBINSON, SALEM*, SEQUOYAH*, SURRY, TAKAHAMA*, TURKEY POINT*,
WESTINGHOUSE WISC-MICH POWER*
- Sites added from previous notification Flowserve US Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.Jlowserve..Gom Page 5 of 5
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FLOWSERVE Flow Control Division Edward Valves
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'2..: ofbf Fax To: US NRC Document Control Desk From: Flowserve Corp Fax: 301-816-5151 Pages: 6 including cover
,.r Phone: 301-816-5100 Date: July11,2017 Re: 10 CFR Part 21 Notification Letter of February 25; 2013 o urgent D For Review . 0 Please Comment D Please Reply* D Please Recycle
- Comments:
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